1. Field of the Invention
The present invention relates to a discharge control unit that is capable of being preferably used for an ion projection unit in an atmosphere in which ions can be generated, and capable of controlling ultraviolet ray projection in a plasma state in an inactive gas atmosphere and discharge of thermoelectrons in a vacuum state, a method for controlling discharge of the same, and a method for producing the same.
2. Description of the Related Art
In recent years, an electrostatic latent image forming system based on an ion projection system which is different from an electrophotography system has been developed (For example, refer to The Institute of Image Electronics Engineers of Japan, Journal Vol. 11, No. 5 (1982), Pages 364 through 369).
Although, in the electrophotography system, an electrostatic latent image is formed on a photosensitive body operating as an image carrier in compliance with two processes consisting of uniform electrification and exposure, the ion projection system is capable of completing formation of an electrostatic latent image by selectively electrifying (electrifying for formation of an electrostatic latent image) an image carrier (the carrier may be any insulative body, which is not necessarily a photosensitive body) only by one process of projection of ions generated in line with discharge from a discharge electrode in an atmosphere in which ions can be generated. Therefore, the ion projection system is a further simplified electrostatic latent image formation system.
For example, in an electrostatic plotter of an ion projection system, a discharge control unit controls ON and OFF of discharge is emitted, projects ions by carrying out discharge from a needle electrode operating as a discharge electrode, and forms an electrostatic latent image on an electrostatic recording sheet of paper whose surface is made insulative.
In a prior art discharge control unit used for the electrostatic plotter, high voltage of several kVpp is selectively applied to respective discharge electrodes (needle electrodes) by a discharge control portion, and discharge is brought about. In order to control ON and OFF of the discharge, a driver IC to cope with high voltage (for example, the control is carried out at 300V through 1000V in a positive or negative state) is employed.
However, there is a problem in that, since it is necessary to widen the spacing of respective discharge electrodes (needle electrodes) to which high voltage is applied, the discharge electrode portion is made large-sized. Also, in order to apply high voltage to the respective driver ICs, it is necessary to secure sufficient distances for the spacing along which the driver ICs are disposed, and for the spacing between lead patterns extending from the respective driver ICs. Therefore, there is another problem in that the discharge control portion is made large-sized. In addition, since the driver IC to cope with high voltage is expensive, there is still another problem in that the discharge control unit and an image forming apparatus employing the same are necessarily made expensive.
An ion generation unit having a discharge electrode and an induction electrode between which a dielectric intervenes, in which pulse waveform voltage of either one of a positive or a negative polarity is applied between the discharge electrode and the induction electrode, according to Japanese Unexamined Patent Publication No. 2003-249327 that has been invented and filed by the present applicant et. al., is capable of applying voltage only with a single power source, is inexpensive, and does not use any alternate current. Therefore, since a current flowing in the dielectric becomes very slight, the consumption power can be reduced, and ions can be generated with comparatively small voltage, wherein the unit brings about excellent actions and effects by which an inexpensive power source having slight consumption power can be used. However, the ion generation unit uniformly electrifies and de-electrifies the entire surface of a photosensitive body and a dielectric of an electrophotography recording unit and an electrostatic recording unit. Therefore, the unit cannot be used as a print head as it is.
Provisionally, if the ion generation unit according to Japanese Unexamined Patent Publication No. 2003-249327 is used as a print head, it is necessary that the discharge electrode is completely divided into a plurality, and discharge can be selectively carried out from the respective discharge electrodes. As a result, problems similar to those of the discharge control unit used for the above-described electrostatic plotter occur.
In order to solve these problems, Japanese Unexamined Patent Publication No. 2003-326756 that the applicant filed after whole-hearted research, discloses an ion generation unit for controlling generation of ions based on control of the temperature of a discharge electrode portion, in which a discharge electrode and an induction electrode are disposed with a dielectric intervened therebetween, an heat-generating element is provided to cope with the discharge electrode, the temperature of the discharge electrode is controlled, adequate high voltage is applied between the discharge electrode and the induction electrode, and discharge of the discharge electrode is controlled by heating of the heat-generating element.